<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        document.querySelector('').addEventListener('click', ()=>{})
        // function fn () {
        //     console.log(1)
        // }

        // function t(a){
        //     a()
        // }

        // t(fn)
        // setTimeout(function(){}, 100)
        // setTimeout(fn, 1000)
        const arr = [1,2,3]
        const fn =  (item) => {
            console.log(item)
        }
        arr.forEach(fn) // map, filter, reduce, find, sort ....
    </script>
</body>
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